Canterbury
Slabs of rock embedded vertically in the soil form the latest addition to the Christchurch Botanic Gardens’ 80-year-old rock garden.
Mary Lovell-Smith visits Christchurch Botanical Gardens’ new crevice garden.
With crevice gardening gaining popularity around the globe, several public ones do exist, but this is a first for New Zealand and was created in conjunction with the
New Zealand Alpine Society.
To oversee its construction, the society brought out renowned crevice garden designer Kenton Seth from Colorado – not uncoincidentally, one of America’s most mountainous states.
Kenton, who has a degree in sculpture, describes himself as a “lifelong gardener and plant nut”, with a particular interest in finding more plants for unirrigated landscapes. He has more than 40 private and public crevice gardens to his name.
A crevice garden is perhaps best described as being a more evolved style of rock garden.
Generally, it is formed by burying flat pieces of stone upright and close together, and the ensuing deep crevices are filled with a free-draining soil or medium in which plants are grown.
Aesthetically, these gardens are quite dramatic, says Kenton. “They’re like a mini mountain range in a garden.”
Indeed, there is definitely a mountain vibe at the new one at the Christchurch gardens, even though it is for the main part only three or so metres long by two or so metres wide (and an irregular shape) and rising to a metre or so high. The sharp-edged rocks jam-packed in offer a higher rock-to-soil ratio than conventional rock gardens. And as anyone who has
been high on a mountain will know, soil is usually in short supply at heights. In the centre of the beds, just the tops of the rocks are visible; elsewhere they are jagged and precipitous outcrops forming the sides.
Horticulturally, crevice gardening forces plant roots to go deeper, Kenton says, thus increasing their access to moisture and nutrients, which for many plants come from rocks rather than soil.
The microclimate created provides a cool, moist place for the roots to grow, with any water funnelled down along the rocks, while the top of the plant stays dry.
The Christchurch garden will be home to what Kenton describes as “a really handsome” collection of crevice plants that will bloom for every month of the year. “They come from anywhere on the planet where there are rocks, so it’s an international buffet of plants.”
It is not just alpines that lap up life in crevices though.
Desert and cliffdwelling plants also love this environment. Consider, too, the myriad little treasures which pop up in cracks in pavements and paths, and in stone walls, which offer similar habitats.
Actually, nor do the rocks have to be mountainous in origin, or even natural rock. In Christchurch they used Halswell stone, a fine-grained, dense black basalt from the western slopes of the Port Hills, but a variety of stone and other materials can be used for the same effect, from demolition concrete to ceramic tiles.
While the quintessential crevice garden attempts to be naturalistic, contemporary versions pay homage only to their spirit, with some having a minimalist aesthetic favouring straight lines and regimented plantings. And as Kenton says: “They don’t have to be huge, monumental things either, just a few rocks pushed together or even a container size can work well.
“You can use them in place of a retaining wall so they’re not just for botanic gardens, they’re for home gardeners as well.”
Kenton has tips for the domestic gardener wanting to create a crevice garden.
Choose a site away from trees, so there is no competition from nearby roots; and never skimp on rocks – a crevice garden would use far more of them than a conventional rock garden – and cram the rocks together.
As well, some proponents say the crevice should be no more than 3cm wide.
If you do make one, you’re continuing a tradition of rock gardening dating back to early Chinese and Japanese culture. Crevice gardens are relative newbies in the genre, dating back only to the 1980s, with the popularly acknowledged founders, patrons, lords – call them what you will – being two
Czechs, Zdenek Zvolanek and Josef Halda.
Zdenek has written a seminal book on the subject ( The Crevice Garden and
Its Plants) and, like Josef, has overseen the design and construction of many important crevice gardens around the world.